Aromatic polycarbonates have excellent mechanical properties such as impact strength, heat resistance, transparency and the like, and are widely used to applications such as various machine parts, optical discs and automobile parts.
A method of directly reacting bisphenols such as bisphenol A and phosgene (interfacial method) and a method of polycondensation reacting bisphenols such as bisphenol A and carbonic diesters such as diphenyl carbonate by an ester exchange reaction (melt process) are known as production methods of such aromatic polycarbonates. Above all, the melt process by an ester exchange reaction has the advantage that aromatic polycarbonates can be produced inexpensively as compared with the interfacial method.
By the way, aromatic polycarbonates are used to many applications, and therefore it is necessary to produce plural kinds of aromatic polycarbonates. On the other hand, when aromatic polycarbonates are produced by the above-described melt process, the production is generally conducted using a production apparatus comprising plural reactors which are connected in series under reduced pressure. Therefore, where reaction conditions such as molar ratio of starting materials charged are changed, changeover loss is generated until obtaining the desired kind of an aromatic polycarbonate.
As a method of diminishing such a changeover loss and quality deterioration, a method of continuously producing plural kinds of aromatic polycarbonates is reported, comprising in a production apparatus comprising plural reactors which are connected, polycondensing bisphenol A and diphenyl carbonate in a previous stage reactor (first stage polymerization step), and pluralizing polycondensation reaction (late polymerization step) subsequently conducted (see Patent Document 1).    Patent Document 1: JP-A-2004-26916